Electric heater assembly



April 23, 1963 J, MGORLLY ELECTRIC HEATER ASSEMBLY Filed 001;. 8, 1958 il l.

INVENTOR. JosfPu MC ORLLY United States Patent Oice 3,087,134 Patented Apr. 23, 1963 3,087,134 ELECTRIC HEATER ASSEMBLY Joseph McOrlly, Wilkinsbnrg, Pa., assignor to Edwin L. Wiegand Company Filed Oct. 8, 1958, Ser. No. 765,972 1 Claim. (Cl. 338-273) The present invention relates to electric resistance heaters, more particularly to electric resistance heaters of the type which are hermetically sealed to prevent communication of lluids and the lik-e` between the interior and exterior thereof, and the principal object of the invention is to provide new and improved heaters of the character described.

In the manufacture of certain kinds of hermetically sealed electric resistance heaters, a problem arises because of differential expansion and contraction of various heater assembly parts, either during the manufacturing process or during use of the heater assembly. As a result of such dilerential expansion and/ or contraction, the current conductive means which carries electrical energy `from a source exteriorly of the heater to the heat generating resistor element within the heater is frequently damaged.

Under certain circumstances, the current conductive means may be tensioned so greatly that it is pulled apart, thus destroying the electrical continuity of the heater. This is especially true when the current conductive means is formed of two or more parts which are welded or otherwise secured together. More frequently, however, the current conductive means is subjected to compressive forces which caused it to buckle. As a result of such buckling, the current conductive means is displaced from its desired position with a resulting loss in dielectric clearance between adjoining heater parts. This loss in dielectric clearance frequently causes short circuiting and resultant destruction of the heater.

The present invention eliminates the problem hereinbefore mentioned in heaters of the type contemplated. Other `advantages will readily become apparent from a study of the following description and from the drawing appended hereto.

In the drawing accompanying this specification and forming a part of this application there is shown, for purpose of illustration, an embodiment which the invention may assume, and in this drawing:

FIGURE 1 is a broken elevational view of an electric resistance heating element embodying the invention,

FIGURE 2 is a broken, enlarged, longitudinal sectional view of the heater seen in FIGURE l, and

FIGURE 3 is a view similar to FIGURE 2 but showing the heater during an intermediate stage of manufacture.

With reference to FIGURES l and 2, the heater chosen to illustrate the present invention comprises an elongated, tubular metallic sheath filled with electric insulating material in which is embedded a coiled resistor conductor 12. One end of the sheath is closed by welding a plug or the like 13 therein. The opposite end of the sheath, through which electrical energy is conducted to the resistor 12, is closed by an enlarged, hollow, closure assembly 14. As will later be described in detail, this closure assembly is welded to the adjoining sheath end to provide a hermetically sealed, unitary structure therewith.

Means are provided for conducting electrical energy from the exterior of the closure assembly, through its hollow interior, and to the coiled resistor within the interior of the sheath. At the present time, such means comprises a pair of current conductors 15, 115 in spaced, side-by-side relation each having its right end (in the position of parts shown) electrically connected with a respective end of the coiled resistor 12 and its left end extending through a wall of the closure assembly for connection to a source of electrical energy.

The sheath 10 and its associated parts are well known in the art; accordingly it should suice to disclose that this portion of the assembly is formed by disposing the coiled resistor 12, which has a terminal conductor pin or the like 16, 116 secured to respective ends thereof, within the sheath whereby the resistor 12 is spaced from the ends of the sheath and whereby the pins 16, 116 project beyond one end of the sheath in spaced, side-by-side relation. The sheath is then filled with a suitable material 11 such as powdered magnesium oxide or filled in whole or in part by bushings formed of the same or similar material. The sheath is then subjected to a swaging operation or the like which reduces its transverse size so as to -compact the material 11 to rock-like hardness. This swaging operation anchors the resistor 12 and the pins 16, 116 in position within the sheath to provide a unitary assembly as is well known to those skilled in the art.

Part of the material 11 may then be removed from the right end (in the position of parts shown) of the sheath 10 and the metal plug 13 then inserted therein. The .plug and the sheath may then be circumferentially welded together at 17 to hermetically close this sheath end.

Returning now to the closure assembly 14, the latter comprises a tubular body 18 presently having an externally threaded portion 19 'and an internally threaded portion 20 spaced axially of portion 19. A transverse wall 21, spaced intermediate the ends of the tubular body, `blocks off its interior as shown.

Presently threaded into portion 20 of body 18 is one end of a sleeve 22. The other end of the sleeve is reduced in size to closely t the exterior of the sheath 10. Sleeve 22 is adapted to be circumferentially welded to body 18 at 23 and to sheath 10 at 24 to provide leak-proof joints thereat. From the foregoing, it will be seen that the closure assembly 14 (comprising body 18 and sleeve 22) cooperates with the left end of the sheath 10 to provide an internal cavity 25 in which the projecting ends of the terminal conductor pins 16, 116 are disposed.

Wall 21, it will be seen, in part defines a wall of the cavity 25 and is provided with a pair of spaced apertures 26, 126. Extending through respective apertures 26, 126 for ultimate connection to a source of electrical energy lare respective conductors 27, 127 which form a part of respective current conductors 15, hereinbefore mentioned. Any suitable means may be provided for securing respective conductors 27, 127 to wall 21 in hermetically sealed, electrically insulated relation. Since the same construction is employed to connect both conductors t0 the wall, la description of the construction as applied to conductor 27 alone should suffice for both.

Conductor 27 presently extends through and is herein shown hermetically sealed to an elongated dielectric sleeve 28 which may be formed of ceramic or other rigid, temperature resistant, non-electrical conductive material. An apertured, cup-shaped member 29 is suitably bonded to the exterior of an intermediate portion of sleeve 28 `and member 29 is brazed or the like at 30 to the portion of wall 21 margining aperture 26. A member 31 similar to member 29, may be seated over the right-hand end of sleeve 28 and may be welded, crimped, or otherwise secured to the adjoining portion of the conductor 27.

As seen in FIGURE 2, the right-hand ends of conductors 27, 127 are adapted to be disposed within cavity 25 adjacent to but spaced from respective terminal pins 16, 116. The means provided for bridging the gap between conductor 27 and pin 16 presently comprises a flexible electrical conductor member 32 which forms an expansile-contractile portion or extension of the conductor 27 `and which may be welded or otherwise secured to conductor 27 `at 33 and to pin 16 at 34. An identical construction employing a member 132 is employed to connect conductor 127 and pin 116 as will be apparent.

At the present time, member 32 comprises a flexible metallic strip formed to provide a loop. It will readily be understood that member 32, being flexible, provides a lost-motion connection which will absorb relative movement between respective ends of the current conductor 15 of which it forms the intermediate part. Obviously, member 32 could be formed to provide a plurality of loops or perhaps formed to a helical configuration. It might also be formed of, for example, a flexible wire instead of the strip illustrated. Any other suitable construction may be employed so long as it provides a yieldable, current conductive junction between respective ends of the current conductor 15. It might also be mentioned that member 32 might, if desired, be formed as an integral part of either pin 16 or conductor 27 instead of being a separate member as herein disclosed.

As illustrated in FIGURE 3, assembly of the foregoing will be as follows: The completed heater, with the terminal pins 16, 116 projecting from one end thereof, will first be assembled with the completed body 18 by welding members 32, 132 to respective terminal pins 16, 116. Members 32, 132, it will be understood, preferably having been earlier welded to respective conductors 27, 127. Sleeve 22 will then be slid over the heater sheath and threaded into portion 20 of the body 18. Next, sleeve 22 will be welded to body 18 at 23 as heretofore disclosed and thereafter, the sleeve will be welded to the heater sheath at 24 to thus form a structurally integral, hermetically sealed assembly between the heater sheath 10, the body 18 and the sleeve 22.

It will be understood that during the making of weld 23, sleeve 22 will become quite hot and will therefore expand in length. This expansion in length will be followed by a corresponding contraction when the sleeve cools; however, since the sleeve is welded to the sheath 10 at 24 following the making of weld 23, the contraction of the sleeve will draw body 18 toward the adjoining end of the sheath. Since conductors 27, 127 are anchored to the body 18 and the terminal pins 16, 116 are anchored to the sheath 10 (by virtue of being embedded in the compacted material 11) the conductors and the terminal pins will be drawn toward each other. Were it not for the lost motion connection provided by the flexible members 32, 132, the terminal pins, being weaker `than the conductors 27, 127, would buckle and possible short out either lagainst each other or against the sleeve 22.

In the event weld 24 is made prior to making weld 23, expansion of the sleeve 22 will tend to move the conductors 27, 127 away from the terminal pins thus tending to rupture the welded joint therebetween. Here again, however the flexible members 32, 132 will absorb the motion harmlessly.

In view of the foregoing it will be apparent to those skilled in the art that 1 have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described, hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited there- 10.

I claim:

A sealed electric heater assembly, comprising a tubular metal sheath hermetically sealed at one end and having its other end open, -a resistance conductor within said sheath and having a pair of terminals accessible at said open sheath end, granular refractory material compacted within said sheath and embedding said resistance conductor, a tubular metal body having an interior transverse wall intermediate its ends and having external screw threads at one end and internal screw threads at its other end, a pair of current conductive posts extending in hermetically sealed relation through respective openings in said wall, each having one end part accessible from the externally threaded end of said body for connection to a source of current and an `opposite end part extending from the internally threaded end of said body, a metal sleeve having a large end externally threaded and fitting the internal threads of said tubular body and a weld to hermetically seal such threaded connection, said sleeve having a small end enclosing and hermetically welded to the open end of said sheath, said sleeve combining with said tubular body to form a closed hermetically sealed chamber into which said resistance conductor terminals and said current conductive posts extend with respective ends in spaced relation, and a pair of metal connectors, each electrically and mechanically connected to ends of respective terminals and posts and bridging the space therebetween, each metal connector having a looped portion freely disposed within said sealed chamber to absorb movement of said posts and said terminals caused by differential expansion fand contraction of various heater parts.

References Cited in the le of this patent UNITED STATES PATENTS 1,638,829 Colby Aug. 16, 1927 1,644,911 Braun Oct. 11, 1927 2,046,102 Abbott June 30, 1936 2,058,769 Brown Oct. 27, 1936 2,154,685 Lamb Apr. 18, 1939 2,265,821 Siegel Dec. 9, 1941 2,372,840 Mattern Apr. 3, 1945 2,669,636 Rawles Feb. 14, 1954 

